A steady speed is key to the marathon.
In the first 30km of the 42.195km race, most athletes choose to follow the group and break ahead thereafter.
Top athletes do not run more than 2-3 marathons a year as running the distance on asphalt is very demanding on the body.
Training for this event includes running distances of 200km per week but also speed and interval training.
Temperature, humidity, wind speed ... everything comes into play in this race, which is the ultimate test of endurance in athletics.